`strncpy` is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

ethtool_sprintf() is designed specifically for get_strings() usage.
Let's replace strncpy in favor of this more robust and easier to
understand interface.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
Note: build-tested only.
---
 drivers/net/dsa/realtek/rtl8366-core.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/net/dsa/realtek/rtl8366-core.c b/drivers/net/dsa/realtek/rtl8366-core.c
index dc5f75be3017..b13766a3acbb 100644
--- a/drivers/net/dsa/realtek/rtl8366-core.c
+++ b/drivers/net/dsa/realtek/rtl8366-core.c
@@ -395,16 +395,13 @@ void rtl8366_get_strings(struct dsa_switch *ds, int port, u32 stringset,
 			 uint8_t *data)
 {
 	struct realtek_priv *priv = ds->priv;
-	struct rtl8366_mib_counter *mib;
 	int i;
 
 	if (port >= priv->num_ports)
 		return;
 
 	for (i = 0; i < priv->num_mib_counters; i++) {
-		mib = &priv->mib_counters[i];
-		strncpy(data + i * ETH_GSTRING_LEN,
-			mib->name, ETH_GSTRING_LEN);
+		ethtool_sprintf(&data, "%s", priv->mib_counters[i].name);
 	}
 }
 EXPORT_SYMBOL_GPL(rtl8366_get_strings);

---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231009-strncpy-drivers-net-dsa-realtek-rtl8366-core-c-60a0f0ddc5cc

Best regards,
--
Justin Stitt <justinstitt@google.com>

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 09 Oct 2023 22:47:37 +0000 you wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
> 
> ethtool_sprintf() is designed specifically for get_strings() usage.
> Let's replace strncpy in favor of this more robust and easier to
> understand interface.
> 
> [...]

Here is the summary with links:
  - net: dsa: realtek: replace deprecated strncpy with ethtool_sprintf
    https://git.kernel.org/netdev/net-next/c/b0e4a14f5ba1

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

On Mon, Oct 09, 2023 at 10:47:37PM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
> 
> ethtool_sprintf() is designed specifically for get_strings() usage.
> Let's replace strncpy in favor of this more robust and easier to
> understand interface.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>
> ---
> Note: build-tested only.
> ---
>  drivers/net/dsa/realtek/rtl8366-core.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/drivers/net/dsa/realtek/rtl8366-core.c b/drivers/net/dsa/realtek/rtl8366-core.c
> index dc5f75be3017..b13766a3acbb 100644
> --- a/drivers/net/dsa/realtek/rtl8366-core.c
> +++ b/drivers/net/dsa/realtek/rtl8366-core.c
> @@ -395,16 +395,13 @@ void rtl8366_get_strings(struct dsa_switch *ds, int port, u32 stringset,
>  			 uint8_t *data)
>  {
>  	struct realtek_priv *priv = ds->priv;
> -	struct rtl8366_mib_counter *mib;
>  	int i;
>  
>  	if (port >= priv->num_ports)
>  		return;
>  
>  	for (i = 0; i < priv->num_mib_counters; i++) {
> -		mib = &priv->mib_counters[i];
> -		strncpy(data + i * ETH_GSTRING_LEN,
> -			mib->name, ETH_GSTRING_LEN);
> +		ethtool_sprintf(&data, "%s", priv->mib_counters[i].name);
>  	}

Nitpick, you don't need to resend for this. But if there's just a single
line remaining in the "for" loop, you could have dropped the braces too.

>  }
>  EXPORT_SYMBOL_GPL(rtl8366_get_strings);
> 
> ---
> base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
> change-id: 20231009-strncpy-drivers-net-dsa-realtek-rtl8366-core-c-60a0f0ddc5cc
> 
> Best regards,
> --
> Justin Stitt <justinstitt@google.com>
> 

Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>

On Tue, Oct 10, 2023 at 12:47 AM Justin Stitt <justinstitt@google.com> wrote:


> `strncpy` is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
>
> ethtool_sprintf() is designed specifically for get_strings() usage.
> Let's replace strncpy in favor of this more robust and easier to
> understand interface.
>
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>
(...)
> -               mib = &priv->mib_counters[i];
> -               strncpy(data + i * ETH_GSTRING_LEN,
> -                       mib->name, ETH_GSTRING_LEN);
> +               ethtool_sprintf(&data, "%s", priv->mib_counters[i].name);

Not only does it harden the kernel, it also makes it way easier to read!

Way to go.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij

On 10/9/23 15:47, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
> 
> ethtool_sprintf() is designed specifically for get_strings() usage.
> Let's replace strncpy in favor of this more robust and easier to
> understand interface.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>

Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
-- 
Florian